(NaturalNews) The evolutionary claims of Paleo Diet proponents do not hold water, according to a paper published by researchers from the University of Chicago in the Quarterly Review of Biology. Instead, evidence from a wide variety of disciplines suggests that carbohydrates from starchy vegetables formed an important part of our evolutionary ancestors' diet.

In fact, carbohydrate consumption was probably a major driver of the enormous growth undergone by the human brain, particularly over the last million years.

In a blow to proponents of a strict raw diet, the study also emphasized the evolutionary importance of cooked vegetables.

"Eating meat may have kick-started the evolution of bigger brains, but cooked starchy foods together with more salivary amylase genes made us smarter still," the researchers wrote.

Paleo Diet only tells part of the story

The highly popular Paleo Diet suggests that optimal health can be achieved by following a diet similar to the one consumed by our recent ancestors in the Paleolithic era, which is presumably the diet that our bodies evolved to eat. The Paleo Diet encourages the consumption of meat, seafood, nuts, seeds, fruits and vegetables while discouraging the consumption of processed foods, dairy and starches.

According to the new study, this narrative overlooks the evolutionary importance of carbohydrates from starchy vegetables. The Paleo Diet shouldn't shoulder all of the blame for this school of thought; much evolutionary research has made the same mistake. In the past few decades, the scientific community has reached a consensus that dietary changes played an important role in the evolution of the human brain over the past 3 million years. However, papers on the topic have largely focused on increased meat in the diet to the exclusion of other foods.

"Up until now ... the importance of carbohydrate, particular in form of starch-rich plant foods, has been largely overlooked," the researchers wrote.

Starches are brain food

In the new study, the researchers reviewed findings from anatomical, anthropological, archaeological, genetic and physiological studies on the importance of carbohydrates to Paleolithic-era humans. They found five major lines of evidence to support their hypothesis that starch consumption combined with cooking fueled human brain consumption over the past 1-2 million years:

The brain uses about 25 percent of the body's energy and 60 percent of its supply of glucose. These energy needs could not have been met on a low-carb diet like the Paleo Diet. While the body can produce glucose from non-carbohydrate energy sources, these processes are energy intensive and are clearly designed as backup systems for times of food scarcity.

The body's glucose needs increase even more during pregnancy and lactation. Low blood glucose levels in pregnant women have been shown to be dangerous to the health of both mother and child.

Studies have shown that starchy food sources were abundant in the habitats occupied by ancestral humans. These sources include tubers, seeds and certain nuts and fruits.

Although the human body has trouble digesting many raw starches, these foods become much easier to digest when cooked. Archaeological evidence suggests that humans have been engaging in this practice for a very long time.

Amylase, an enzyme found in saliva, is used to break down starch to ease its digestion. While all other species of primates carry two copies of salivary amylase genes, humans carry an average of six. This means that human saliva has much higher levels of amylase and human are much better at digesting starch. Genetic data suggests that the extra salivary amylase genes entered the human genome within the last million years.

Taken together, the researchers write, this data suggests that glucose has played a key role in the human diet - particularly the development of the human brain - over the last 800,000 years.